This invention relates to the field of parameter sensors. More particularly, this invention relates to the field of borehole sensors where parameters in a borehole, particularly a gas or oil well, are sensed and transmitted to the surface.
In the field of oil and gas drilling, the usefulness of a system capable of detecting certain parameters at the bottom of the drill string and transmitting such data to the surface during the course of drilling has long been recognized. Several systems have been proposed for accomplishing such sensing and data transmission. One of the principal types of such systems is the mud pulse telemetry system wherein pulses are generated in the mud column in the drill string for transmission of data to the surface. The present invention is particularly adapted for use in mud pulse transmission systems.
While some proposals and systems for borehole telemetry have involved arrangements where sensor packages are periodically lowered into and raised from a well hole, by far the most preferred arrangement is to have the parameter sensing apparatus permanently positioned at the bottom of the well, preferably in a lower segment of the drill string. The permanent down hole position of the parameter sensors does, however, make the factors of reliability, accuracy and repeatability of parameter operation all the more important. Otherwise, the driller does not have a truely accurate indication of the direction of the well hole if the parameter sensors are not highly accurate, or serious loss of time and expense may be involved if it is necessary to remove the drill string at unscheduled times.